Implants aid weight loss in mice

As the guilt of an overly indulgent weekend kicks in, the chances are that many individuals are resolving to apply more willpower when it comes to tasty treats. If only there were an implant that could trigger a satiety signal in the body so that the desire to overeat would just disappear.

And while this might sound like a dieter's dream, researchers from the Department of Biosystems Science and Engineering in Basel, Switzerland, believe they are getting closer to making this a reality.

According to the World Health Organization (WHO), over half of the population in many industrialized nations is overweight, with one in three people being obese. And the health implications are also huge.

The Centers for Disease Control and Prevention (CDC) says heart disease, stroke, certain types of cancer and type 2 diabetes are just some of the potential hazards an obese person may have to face.

The CDC also estimates that in monetary terms, obesity costs the US dear. In 2008, the organization claims the figure of $147 billion, stating the costs of treating people who are obese are, on average, $1,429 higher than for people of a healthy weight.

Part of the problem, the researchers say, is that not only does a high-calorie, high-fat diet tend to linger on the hips, backside and belly, it also leaves traces of the ingested fats in the blood. Higher blood-fat values are regarded as risk factors for heart attacks and strokes.

So, back to Switzerland, where Prof. Martin Fussenegger and his team believe they have come up with something that not only works as an early warning system, but also can supply the remedy before the problem gets out of hand.

Designer genes

They have constructed an implantable closed-loop genetic circuit, made mainly from human gene components, which monitors the levels of fats circulating in the blood.

The device also has a feed-back function that responds to excessively high levels of fat in the blood and triggers the supply of a "messenger substance" that makes you feel full and satisfied - in this case, the clinically licensed appetite-suppressing peptide hormone pramlintide.

Pramlintide works by reducing the absorption of glucose and fats by slowing gastric emptying and triggering receptors in the satiety center of the hypothalamus.

These tiny devices were then implanted into human cells, which were in turn inserted into tiny capsules. For the research, these capsules were then implanted into obese mice that had been fed a high-fat diet.

Implanted designer cells engineered with a synthetic anti-obesity gene network constantly score the blood-fat level of the animals and coordinate them to suppress appetite.
Graphics: M. Fussenegger. Photo: Jackson Lab

The researchers found that as soon as the implants registered excessive levels of fat in the blood and triggered the release of pramlintide, the mice stopped eating and their body weight dropped. Once the fat levels returned to normal, the device stopped producing the satiety signal.

"The mice lost weight although we kept giving them as much high-calorie food as they could eat," Prof. Fussenegger explains.

The research says that the animals ate less because the implant signaled a feeling of satiety to them.

The Swiss team is excited about the possible implications of such a device - particularly its ability to monitor many different types of fat in the blood at one time. However, they warn it will take years before such a device is ready for human use.

Looking to the future, Prof. Fussenegger hopes that one day it could be an alternative to surgery, such as liposuction or gastric bands - surgeries that are rapidly gaining popularity.

Prof. Fussenegger says:

"The advantage of our implant would be that it can be used without such invasive interventions."

Another advantage of this implant is that by exploiting the human satiety mechanism, it has a preventative effect, tackling the problem at its source instead of intervening when the disease has progressed.

Written by Belinda Weber

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